What type of mesh are you trying to use? Hexahedral? Tet? Structured? Will you use map, submap, cooper? You may need to tweak your geometry a little bit in order to get Gambit to mesh your flow domain the way you want.

When i a substractin the volume , and tryin to mesh with a tetra/hyb , type Tgrid , i got the mesh for the brick only , with no space inside it (so there is no hollow inside the brick that represent the subtracted sphere ); i will aaprecitae ur reply as soon as possible!

Since you are dealing with regular geometries, you should be able to create in Gambit a 'real' brick and sphere and subtract one from the other. You can now mesh this composite subtracted volume without any hassles.